A light beam heating apparatus which heats up a local spot without touching the local spot is widely used for soldering small size electronic components. Wire solder or cream solder is used in general when the light beam heating apparatus is employed. A conventional feeder of wire solder employed in a soldering machine is described with reference to FIG. 4A and FIG. 4B.
FIG. 4A shows an entire structure of the conventional feeder, and FIG. 4B shows an essential part thereof.
In this conventional feeder of wire solder, wire solder detector 2 monitors whether wire solder 1 travels to feeding roller 3 normally free from discontinuation, and then roller 3 feeds wire solder 1 into guide tube 7a. Part of guide tube 7a is cut away, and wire solder 1 is exposed therefrom. The exposed wire solder 1 contacts shaft 5a of rotary disc 4a. The travel of wire solder 1 drives shaft 5a, which is integrated with disc 4a, and then disc 4a also rotates. The rotation of disc 4a is converted into a detection signal by rotation sensor 4b. This electric signal is sent to feeding controller 6, which sends a rotation instructing signal to a motor 9 that drives feeding roller 3.
When wire solder 1 normally travels, the detection signal by sensor 4b synchronizes with the rotation instructing signal supplied to motor 9. When wire solder 1 is at a normal halt status, the detection signal also synchronizes with the rotation instructing signal. Feeder controller 6 determines whether wire solder is normally fed or at a halt by comparing and calculating the rotation instructing signal and the detection signal converted by sensor 4b. If some abnormality occurs in the feeding of wire solder 1, the two signals do not synchronize with each other. Then controller 6 determines that some abnormality has occurred in the feeding, and immediately stops sending the rotation instructing signal to motor 9. After passing through guide tube 7a, wire solder 1 travels into feeding-direction-fine-adjuster 8 via feeding tube 7. Adjuster 8 adjusts a feeding direction of wire solder 1, which is then sent to a precise location requiring the soldering.
The conventional feeder, however, has the following problem. In the conventional feeder, the shaft 5a of rotary disc 4a directly contacts wire solder 1, so that the feeding condition of wire solder is detected. The rotational accuracy of disc 4a depends on the friction factor between wire solder 1 and the shaft 5a. The friction factor is determined by the material of wire solder 1 and the material of the shaft 5a. Therefore, wire solder 1 tends to slip on the shaft 5a, which often misleads the controller 6 in determining to stop feeding of the wire solder 1, even though it is normally fed.